Population and virulence factor dynamics in fecalEscherichia colifrom healthy adults consuming weight control diets

Fate of Extended-Spectrum β-Lactamase-Producing Escherichia coli from Faecal Sources in Surface Water and Probability of Human Exposure through Swimming

The goal of this study was to determine the fate of ESBL-producing Escherichia coli (ESBL-EC) emitted from faecal sources in surface water, and the probability of human exposure through swimming. Concentrations of ESBL-EC were measured in recreational waters and in source waters, being water in ditches surrounding poultry farms and municipal wastewater. Additionally, the potential of ESBL-EC in source waters to reach recreational waters located downstream of these sources was modeled. Modeled ESBL-EC concentrations in recreational waters appeared to be mostly determined by the concentrations in the source waters and by subsequent dilution in surface water, and less by inactivation. The mean (95%) risk of human exposure to ESBL-EC per person per swimming event, as assessed from measured ESBL-EC concentrations in recreational waters, was 0.16 (0.89) for men, 0.13 (0.72) for women and 0.20 (0.95) for children. Similar exposure risks were estimated for hypothetical recreational waters containing 100- or 1000-times diluted source water, located 10 days water travel time downstream of the sources. Human exposure to ESBL-EC through swimming is likely, if recreational waters are located downstream of poultry farms and municipal wastewater discharge points.

Effect of diet and gut dynamics on the establishment and persistence of Escherichia coli

Escherichia coli population dynamics and diversity in rats fed diets differing in their crude fibre content were assessed. Female Wistar rats (n = 40) were fed diets containing 1, 4, 18 or 26 % crude fibre. Animals were housed in pairs, and one animal was inoculated with a phylogroup B1 strain of E. coli, the other with a phylogroup B2 strain. Natural strain transmission was allowed to occur between the animals in each cage. As expected, the diets had a significant effect on gut dynamics. Mean gut retention times were shorter in animals fed the 18 and 26 % crude fibre diets compared with animals on the low-fibre diets. The effect of diet on gastrointestinal dynamics in turn affected E. coli population dynamics and clonal composition. Animals fed the low-fibre diets had higher cell densities than animals fed the high-fibre diets. E. coli populations dominated by phylogroup B2 strains exhibited lower cell densities in animals fed the high-fibre diets compared with cell densities in animals fed the low-fibre diets. Overall, E. coli cell densities declined as gut transit times decreased. Results from this experiment support the results garnered from prospective studies examining the distribution of E. coli from hosts with differing diets, gut morphology and dynamics.